It is well known that high molecular weight, aromatic polycarbonate resins have high impact strength below a critical thickness of between about 1/2 and 1/4 inches. Above this average thickness, the impact strength of such polycarbonate resins is low. It is also known that the impact strength of these polycarbonate resins decreases rapidly as temperatures decrease below about -5.degree. C. as well as after aging at elevated temperatures above about 100.degree. C. These characteristics limit the fields of applications of these resins. Thus, unmodified polycarbonates are not practical for use at low or high temperatures when good impact strength is required. Therefore, it is desirable to improve the impact strength of polycarbonate resins at both low and high temperatures as well as improve their aged impact strength and thereby expand the fields of application of such resins.
In copending application Ser. No. 957,801 filed Nov. 6, 1978 U.S. Pat. No. 4,257,937, polyester compositions having improved impact are described. These compositions comprise (a) a polybutylene terephthalate which can also include another polyester copolymer, (b) a polyacrylate, and (c) an aromatic polycarbonate. The amount of polyacrylate employed can range from about 5-20 weight percent while the amount of aromatic polycarbonate employed can range from about 10-20 weight percent. Thus, the primary component in these compositions is the polyester so that the polyacrylate and polycarbonate portions are employed as the modifiers.
Polycarbonate compositions having improved impact strength at both high and low temperatures as well as improved aged impact strength are disclosed in co-pending applications Ser. Nos. 69,822; 69,823; 69,824; and 69,825 all of which were filed Aug. 27, 1979 as well as in co-pending applications Ser. Nos. 132,331; 132,325; and 132,190 filed of even date with this application.